1. Field of the Invention
This invention relates to a thermal transfer recording medium which is usable repeatedly, and more particularly to a thermal transfer recording medium in which the density thereof is not substantially lowered even when used repeatedly and printing can be made with relatively low energy, the speed and density thereof are high and the resolution power thereof is also excellent.
2. Description of the Prior Art
As for the thermal transfer recording media with the purpose of being used well repeatedly, there is, as an example, disclosure of an invention in Japanese Patent Publication Open to Public Inspection (hereinafter called Japanese Patent O.P.I. Publication) No. 68253/1979. The techniques of this invention is that a fine porous layer is made of a resin and the pores thereof are impregnated with a thermally sensitive ink.
Therein, a dye transfer image is substantially low in density, and there is, therefore, required substantially high energy to obtain a high density dye transfer image; and besides the edges of a printed image will lack clearness even if a high density dye transfer image should be obtained by applying to it high energy. Another technique similar to the above is disclosed in Japanese Patent O.P.I. Publication No. 105579/1980 and the same defects are observed therein.
As for the thermal transfer recording media capable of solving the abovementioned defects, there is a technique disclosed in Japanese Patent O.P.I. Publication No. 36698/1982 in which a resin layer is interposed between an ink layer, i.e., a coloring agent layer and a support, and the abovementioned ink layer is impregnated with a low melting resin having the softening or melting point of from 60.degree. to 120.degree. C. According to this technique, the adhesion of the ink layer to the support may be improved and high density printing may certainly be performed by using relatively low energy; however, to the contrary, this thermal transfer recording medium has such defect that a dye transfer image is so seriously lowered in density, that it is of no practical use.